Clearing Canvas

[Tim_Buktu]

Hi, quick question: I am trying to draw a multigraph on a canvas in a loop, which means it should always delete the previous plot before drawing the new ones on the canvas. My code looks something like this:

....
TMultiGraph* multiGraph = new TMultiGraph();

while (true) {

         for (Int_t i = 0; iSample < branchNames.size(); ++i) {
               // get the branch of my tree
              //  get the leaf (each entry is an array of floats)

              // create new graph
}

         for (Int_t j = 0; j < arrayLength; ++j){
             // set points of graph with values of the entry's array
}
            
            // add graph to multigraph
}
               
               multiGraph->Draw("AL");
               canvas->Update()

                ....
                        

So basically each new iteration of the while loop, the canvas should be cleared from the previous plots/graphs. I have tried everything, i.e. putting

multigraph->Clear();

canvas->Clear();

canvas->Modified();

In different combinations in different places of the code but nothing seems to work. It keeps overlaying the plots. The only thing that works is creating a new instance of multigraph each new iteration of the loop. But that does not seem like an efficient elegant way.

[couet]

It is strange the plots are overlayed because the option “A”, when you draw the multipgraph, asks to redefine the axis and produce a new plot. Do you have a simple macro reproducing this effect ?

[Wile_E_Coyote]

multigraph->Clear(); does nothing … you need: delete multigraph; multigraph = new TMultiGraph();

[Tim_Buktu]

Ok I guess I’ll go with this solution. Will the former graphs added in the loop also be deleted from memory when deleting the multigraph?

[Wile_E_Coyote]

The TMultiGraph owns the objects in the list.